import java.util.LinkedList;
import java.util.Queue;

public class MyBinaryTree {
     static class TreeNode{
         public char val;
         public TreeNode left;
         public TreeNode right;
         public TreeNode(char val) {
             this.val = val;
         }
     }
    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        //E.right = H;
        //this.root = A;
        return A;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null){
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    public void inOrder(TreeNode root) {
        if(root == null){
            return;
        }
        preOrder(root.left);
        System.out.print(root.val+" ");
        preOrder(root.right);
    }

    // 后序遍历
    public void postOrder(TreeNode root) {
        if(root == null){
            return;
        }
        preOrder(root.left);
        preOrder(root.right);
        System.out.print(root.val+" ");
    }

    public static int nodeSize;
    /**
     * 获取树中节点的个数：遍历思路
     */
    public void size(TreeNode root) {
        if(root == null){
            return ;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    public int size2(TreeNode root) {
        if(root == null){
            return 0;
        }
        return 1 + size2(root.left)+size2(root.right);
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;
    public int getLeafNodeCount1(TreeNode root) {
        if(root == null){
            return 0;
        }
        if(root.left == null&&root.right == null){
            return 1;
        }
        int leftsize = getLeafNodeCount1(root.left);
        int rightsize = getLeafNodeCount1(root.right);
        return leftsize+rightsize;
    }

    /*
     获取叶子节点的个数：子问题
     */
    public void getLeafNodeCount2(TreeNode root) {
        if(root == null){
            return ;
        }
        if(root.left == null&&root.right == null){
            leafSize++;
        }
        getLeafNodeCount2(root.left);
        getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    public int getKLevelNodeCount(TreeNode root, int k) {
        if(root == null){
            return 0;
        }
        int leftsize = getKLevelNodeCount(root.left,k-1);
        int rightsize = getKLevelNodeCount(root.right,k-1);
        return leftsize+rightsize;
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    public int getHeight(TreeNode root) {
        if(root == null){
            return 0;
        }
        int leftheight = getHeight(root.left);
        int rightheight = getHeight(root.right);
        return (leftheight > rightheight) ? (leftheight + 1):(rightheight + 1);
    }


    // 检测值为value的元素是否存在
    public TreeNode find(TreeNode root, char val) {
        if(root == null){
            return null;
        }
        if(root.val == val){
            return root;
        }
        TreeNode leftnode = find(root.left,val);
        if(leftnode != null){
            return leftnode;
        }
        TreeNode rightnode = find(root.left,val);
        if(rightnode != null){
            return rightnode;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            System.out.print(cur.val+" ");
            if(cur.left != null) {
                queue.offer(cur.left);
            }
            if(cur.right != null) {
                queue.offer(cur.right);
            }
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root == null) {
            return true;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if(cur != null) {
                queue.offer(cur.left);
                queue.offer(cur.right);
            }else {
                break;
            }
        }
        while (!queue.isEmpty()) {
            TreeNode tmp = queue.poll();
            if(tmp != null) {
                return false;
            }
        }
        return true;
    }
}
